1. Field of the Invention
The present invention relates generally to power convertors, and more particularly to a separable engine and gas compressor. The engine-compressor is optimally dampened so as to provide a compact, lightweight, easily repairable unit.
2. Description of the Related Art
The compressor field includes many different inventions which have attempted to combine a power driver, such as an automotive engine or virtually any other engine, including an electric motor, with a compressor, such as a gas compressor, to compress gas. More specifically, these engine-compressor combinations have been either integral or separable. An integral combination means that the engine and compressor are built as one unit by using a common crankshaft connected to pistons that provide drive power or compress gas. Some current manufacturers of the integral design include Ajax, Hurricane and Gas Jack. A separable combination is one that physically separates the power driver or engine from the compressor. The power driver and compressor are joined together by a system of components to allow their functioning together. Separable compressors are the most widely used in the natural gas gathering industry. Ariel and Gemini are two large manufacturers of separable natural gas compressors. Typically the engines used in the separable natural gas design are provided by Caterpillar or Waukesha.
Separable designs do have the nominal advantage of being easier to repair than the integral design. One reason for easier repair is that the power can be separated from the compression function. In addition, the separable design allows for easier power-to-load matching from the engine to the compressor. A separable compressor can also be driven by an electric motor.
Prior art has a long list of problems and disadvantages which the present invention has overcome. One disadvantage in the design of all known previous long-life continuous duty driver-compressor combinations has included a relatively large footprint, necessitated by the massive weight to control vibration. Another disadvantage of the current prior art design is the difficulty in repairing or replacing either the compressor or the driver functions. With any system shutdown, lengthy downtime is experienced because of the required disassembly of much of the structure to isolate the cause of the breakdown. Then additional lengthy delay is typically experienced because the needed part is uniquely designed, thereby requiring even more time to build and ship. Also, the massive weight and design complexity prevent easy portability and use in less-developed countries.
Therefore, it is clear that a need exists in gas compressor markets for an improved separable power driver-compressor combination that is easily and quickly repairable, lightweight, and has a small footprint. The present invention overcomes all these long standing problems and disadvantages of the prior art.
Some of the prior art includes the following U.S. patents. These patents describe converted automobile engines. Jones U.S. Pat. No. 2,133,769, discloses an air compressor based on the V-8 configuration of an automobile engine. This configuration discloses one bank of cylinders as the compressor function and the second bank of cylinders as the driver function. Grimmer U.S. Pat. No. 3,462,074, and Waldrop, U.S. Pat. No. 5,267,843, also disclose integral configuration air compressor designs in which one bank of four cylinders is used for the driver function and the other bank of cylinders is used for air or gas compression.
Dunn, U.S. Pat. No. 5,267,843, discloses an integral air compressor based on a Volkswagen four cylinder horizontally opposed automotive engine. The Dunn compressor is also a low pressure single stage compressor. The Caldwell U.S. Pat. No. 5,400,751, discloses an integral compressor based on a linear cylinder configuration with part of the cylinders functioning as the driver engine and the other cylinders serving as the compressor function. The integral compressor design has several disadvantages. The major disadvantage is that both driver and compressor use a common crankshaft and share the same frame package. When failure occurs, of either the driver or compressor functions, the entire unit is rendered inoperable, requiring complete replacement or repair. The negative consequences of such a failure depend on where and how the compressor is installed. In addition, the operating envelope is more limited than that of a separable compressor in which the size and power of the driver engine is independent of the compressor. An integral compressor is constrained to only operate at the speed of the engine function since the functions share the same crankshaft. This design constraint severely limits the operating envelope of the integral design. In summary, the cited patents all relate to integral engine-compressor art. The present invention relates to a separable driver engine and compressor. Therefore, it appears that the above-mentioned patents are not directly relevant.
Virtually all relevant patent prior art seems to have been issued before 1940. Another U.S. patent, Stone U.S. Pat. No. RE 13,645, issued Nov. 11, 1913, discloses an air compressor comprised of apparatus including a main piston chamber, an annular chamber and a piston with two piston heads. The invention operates to draw in air, circulate it for cooling, and then force it out of an outlet valve. Stone's patent is directed to a different invention than that of the present invention. Another prior art patent, Tenney, U.S. Pat. No. 4,391,568, discloses a gas compressor using air cooling in an apparatus using fins to dissipate heat. Tenney's patent is directed to a different invention than that of the present invention.
Separable compressors are widely used to compress gases. Gas compressors have transported natural gas from the producing wells to consumers through high pressure pipelines for over 80 years. These compressors are needed because the outflow pressure of the vast majority of gas wells is lower than the pipeline pressure. Compressors are also used to equalize gas well pressures for a gathering system that combines multiple well outputs before injecting the gas into the transportation pipelines. Another important use for gas compressors is providing high pressure gas to lift oil from producing zones to the surface through special valves. In recent years multiple stage, high pressure compressors have been used to refuel vehicles that use compressed natural gas as a fuel. All gases including air are commonly compressed with separable compressors.
Ariel and Gemini are two of the largest manufacturers of separable compressor units. Gas compressor designs vary greatly. The most widely used design approach for small to medium size (50 to 5,000 horsepower) gas compressors employs one or more reciprocating pistons. The piston design is used because of the high efficiency and relative simplicity of sealing off the gas, thereby minimizing gas leakage. Numerous companies are producing this type of compressor. The March-April 1998 issue of CompressorTech provides numerous examples of current difficulties in the prior art. In one article, the need for many people trained in preventive maintenance is highlighted in order to achieve a high reliability of operation. The present invention, with its novel modular construction feature, simplifies preventive maintenance and overhauls. The modular construction technique that minimizes the number of compressor parts eases the maintenance burdens and reduces logistics problems. Knox Western, is another manufacturer of separable compressors, as described on page 22 of the March-April 1998 issue of CompressorTech. As is seen in the pictures, the models shown are huge and heavy relative to the Applicant's disclosed invention. The present invention overcomes this disadvantage by providing a relatively lightweight, compact compressor unit. Still another major design and maintenance problem of industrial compressors is highlighted on page 60 of the March-April 1998 issue of CompressorTech. Vibration problems are inherent in the current designs of compressors. Extensive monitoring programs exist, as described, to detect vibration as soon as possible, requiring the compressor to be shut down for maintenance. The present invention exhibits virtually no vibration because of its novel design in eliminating vibration through numerous damping and construction features.
The separable concept of a compressor disclosed herein uses a linear, or in-line, cylinder drive engine powering a separate compressor. Both the engine and compressor are configured from similar volume production piston engine components. There is an advantage to using the same engine for both the driver and the compressor function in order to maximize commonality of parts. The current technology demonstration unit uses a common block design. This preferred concept is useful over a wide range of potential applications. It is only where there is a substantial divergence of engine power envelope and compressor power requirements that a different configuration between the engine and compressor is necessary. The compressor is configured as an automotive engine converted to function as a gas compressor by removing the existing head and valve assembly, and adding only the necessary parts to insure efficient and reliable operation. This compressor unit is also capable of single or multiple stage operation. The separable package basically consists of an engine and a compressor which are joined by an endless belt, chain, or gears, plus structural parts to reduce the vibration to a minimum level as will be described below.
Many of the prior art separable gas compressors use horizontally opposed cylinder designs for the compressor and a relatively large and heavy driver engine. The engine and compressor are joined by a coupling. The disadvantages to this design approach are, first, that the package size of the two separable units is substantially greater than that of the integral compressor, and, second, that the maintenance of the separable units is more difficult because of different designs and parts used in the driver engine and compressor. The present invention overcomes the size and weight disadvantages through efficient packaging and low vibration levels and improves maintainability through maximum commonality of parts.